Solid state image pickup device and method for manufacturing the same

Abstract

To reduce white spots by optimizing an impurity concentration of a p-type impurity doped region of a well contact, a size of a contact portion, a position of an n-type region serving as a photoelectric converter, and so on. In a solid state image pickup device in which a semiconductor substrate 11 includes a pixel region where a plurality of pixels are arranged, each pixel including a photoelectric converter 21 , and a pixel well 12 shared by the respective pixels, a well contact 14 supplying a reference voltage to the pixel well 12 includes: an electrode 15 supplying a reference voltage; a p-type impurity doped region 16 placed in a surface of the pixel well 12 ; and a contact portion 17 placed in the p-type impurity doped region 16 so as to be connected to the electrode 15 and having a higher concentration than the p-type impurity doped region 16 . The p-type impurity doped region 16 is doped with at least a p-type impurity, with an impurity concentration of 1×10 19 cm −3 or less.

1. A solid state image pickup device comprising a semiconductor substrate including (a) a pixel region where a plurality of pixels are arranged, each pixel including a signal charge accumulating portion and one or more transistors, and (b) a peripheral circuit region outside the pixel region,
 wherein the pixel region includes: 
 a pixel well of a first conductive type in the substrate; 
 at least one charge accumulating portion extending in the pixel well; 
 a first impurity doped region of a first conductive type in a surface of the pixel well; and 
 a pixel well contact of the first conductive type in a surface of the first impurity doped region; and 
 wherein:
 the pixel well contact has a higher doping concentration than the first impurity doped region, 
 the at least one signal charge accumulating portion is of a second conductive type, and 
 the at least one charge accumulating portion extends to a point where the pixel well contact overlies the charge accumulating portion. 
 
 
   
   
     2. The solid state image pickup device according to  claim 1 , wherein the first impurity doped region is doped with at least an impurity of the first conductive type and the impurity concentration thereof is 1×10 19  cm −3  or less. 
   
   
     3. The solid state image pickup device according to  claim 1 , wherein the first conductive type is a p-type and the second conductive type is an n-type. 
   
   
     4. The solid state image pickup device according to  claim 1 , wherein the at least one signal charge accumulating portion is isolated from a contact portion. 
   
   
     5. The solid state image pickup device according to  claim 1 , wherein:
 the at least one signal charge accumulating portion includes a surface region of the first conductive type and an accumulating region of the second conductive type disposed under the surface region; and 
 the surface region is part of the first impurity doped region. 
 
   
   
     6. The solid state image pickup device according to  claim 5 , wherein the at least one signal charge accumulating portion extends completely under the contact portion. 
   
   
     7. The solid state image pickup device according to  claim 1 , wherein:
 the peripheral circuit region includes a second peripheral well of the first conductive type; 
 at least one of peripheral contacts via which a reference voltage can be supplied to the second peripheral well comprises, (a) a peripheral electrode via which a reference voltage can be supplied, (b) a second impurity doped region of the first conductive type in a surface of the second peripheral well, and (c) a contact portion of the first conductive type in the second impurity doped region so as to be connected to the peripheral electrode; and 
 an impurity concentration of the second impurity doped region is higher than that of the first impurity doped region. 
 
   
   
     8. A solid state image pickup device comprising a semiconductor substrate including (a) a pixel region where a plurality of pixels are arranged, each pixel including a signal charge accumulating portion and one or more transistors, and (b) a pixel well in the substrate of a first conductive type shared by the respective pixels,
 wherein:
 the pixel region is provided with a pixel well contact via which a reference voltage can be supplied to the pixel well, 
 the pixel well contact comprises (i) an electrode over the pixel well supplying a reference voltage, (ii) a first impurity doped region of the first conductive type placed in a surface of the pixel well, and (iii) a contact portion of the first conductive type placed in a surface of the first impurity doped region so as to be connected to the electrode, the contact portion having a higher doping concentration than that of the first impurity doped region; 
 the first impurity doped region is doped with at least an impurity of the first conductive type and the impurity concentration thereof is 1×10 19  cm −3  or less; and 
 the at least one signal charge accumulating portion extends to a point under the pixel well contact where the pixel well contact overlies the signal charge accumulating portion; and 
 the at least one signal charge accumulating portion is of a second conductive type opposite the first conductive type. 
 
 
   
   
     9. The solid state image pickup device according to  claim 8 , wherein the first conductive type is a p-type. 
   
   
     10. The solid state image pickup device according to  claim 8 , wherein the at least one signal charge accumulating portion is isolated from a contact portion. 
   
   
     11. The solid state image pickup device according to  claim 8 , wherein:
 the at least one signal charge accumulating portion includes a surface region of the first conductive type and an accumulating region of the second conductive type disposed under the surface region, and 
 part of the surface region is part of the first impurity doped region. 
 
   
   
     12. The solid state image pickup device according to  claim 11 , wherein the at least one signal charge accumulating portion extends completely under the contact portion.